title: Distribution and neurochemical characterization of neurons in the rat ventrolateral medulla activated by glucoprivation.
abstract: Hypoglycemia elicits physiological and behavioral responses which are mediated in part by neurons within the ventrolateral medulla (VLM). The present study describes the neurochemistry of neurons activated by glucoprivation (2-deoxy-D-glucose, 2DG), specifically those within regions containing the A1, caudal C1 (cC1) and rostral C1 (rC1) cell groups. 2DG induced c-Fos immunoreactivity throughout the VLM. Activated neurons expressing prepro-cocaine and amphetamine-regulated transcript (PPCART), neuropeptide Y (NPY), glutamic acid decarboxylase (GAD67) or prepro-enkephalin (PPE) mRNA and/or immunoreactivity (-ir) for tyrosine hydroxylase (TH) were identified. TH(+) neurons were recruited in a dose-dependent manner. At high doses of 2DG [400 mg/kg, (n = 6)], 76 ± 1.2 % of activated neurons were TH(+) representing 52 ± 1.3 % of the total TH population. Virtually all activated neurons in the A1 and cC1 regions but only 60 % in the rC1 region were TH(+). Within the A1 region, TH(+), TH(+)NPY(+) and TH(+)NPY(+)PPE(+) subpopulations were activated and likely regulate vasopressin, oxytocin, and corticotrophin releasing hormone (CRH) from the hypothalamus. Within the cC1 region, non-TH neurons, TH(+)NPY(+), TH(+)NPY(+)PPCART(+), and TH(+)NPY(+)PPE(+) subpopulations were activated, likely regulating autonomic hypothalamic neurons or CRH and thyrotropin releasing hormone secretion. Within the rC1 region, non-TH neurons (40 % of those activated) were predominantly PPE(+) and were recruited by higher 2DG doses. Of the TH(+) activated neurons in the rC1 region, many expressed PPCART and half expressed NPY. The activated spinally projecting population was almost entirely TH(+)PPCART(+) and is likely to regulate adrenaline and glucagon release. These data indicate that glucoprivation activates at least nine phenotypically distinct populations of neurons in the VLM.
authors.affiliation: The Australian School of Advanced Medicine, Macquarie University, 2 Technology Place, North Ryde, Sydney, NSW, 2109, Australia.
authors.forename: Lindsay M
authors.initials: LM
authors.lastname: Parker
authors.forename: Natasha N
authors.initials: NN
authors.lastname: Kumar
authors.forename: Tina
authors.initials: T
authors.lastname: Lonergan
authors.forename: Simon
authors.initials: S
authors.lastname: McMullan
authors.forename: Ann K
authors.initials: AK
authors.lastname: Goodchild
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000187:drug effects; D002452:Cell Count; D002772:Cholera Toxin / Q000378:metabolism; D003847:Deoxyglucose / Q000633:toxicity; D004195:Disease Models, Animal; D005786:Gene Expression Regulation / Q000187:drug effects; D005968:Glutamate Decarboxylase / Q000235:genetics / Q000378:metabolism; D007003:Hypoglycemia / Q000139:chemically induced / Q000473:pathology*; D008297:Male; D008526:Medulla Oblongata / Q000473:pathology*; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D009474:Neurons / Q000378:metabolism*; D009478:Neuropeptide Y / Q000235:genetics / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D012333:RNA, Messenger; D051381:Rats; D017207:Rats, Sprague-Dawley; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism; D000098882:Cocaine- and Amphetamine-Regulated Transcript Protein
chemical_list: D001786:Blood Glucose; D009419:Nerve Tissue Proteins; D009478:Neuropeptide Y; D016760:Proto-Oncogene Proteins c-fos; D012333:RNA, Messenger; D000098882:Cocaine- and Amphetamine-Regulated Transcript Protein; D002772:Cholera Toxin; D003847:Deoxyglucose; D014446:Tyrosine 3-Monooxygenase; D005968:Glutamate Decarboxylase; C402565:glutamate decarboxylase 1